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jaw. Finally, JToplophoneus has acquired the dentition of exist-
ing Cats.
The Machaerodons, however, show examples with a yet more
reduced dentition than that of the most reduced existing Cat, viz.
the Lynx, which has only two premolars in each jaw and one molar.
In Eusmilus the molar in both jaws Is single, and there is but
one premolar in the lower jaw.
The genus MacJiaerodus itself, which appears to include
Smilodon, Is referred by Cope to the true Cats, and not to the
Himravidae, as he terms the family which we have called here
the Machaerodontidae. These creatures are known as " Sabre-
toothed Tigers/* and were of very wide distribution, occurring in
South America as well as in Europe and 3STorth America. " A a
nothing," remarks Professor Cope, " but the characters of the canine
teeth distinguished these from typical felines, it is to these that
we must look for the cause of their failure to continue. Professor
Flower's suggestion appears to be a good one, viz. that the
length of these teeth became an inconvenience and a hindrance
to their possessors. I think there can be no doubt that the
huge canines In the Srnilodons must have prevented the biting
off of flesh from large pieces, so as to greatly interfere with
feeding, and to keep the animals in poor condition. The size of
the canines Is such as to prevent their use as cutting instruments
excepting with the rnouth closed ; for the latter could not have
been opened sufficiently to allow any object to enter it from the
front. Even when it opens so far as to allow the mandible to
pass behind the apices of the canines, there would appear to be
some risk of the latter being caught on the point of one or the
other canine, and forced to remain open, causing early starvation.
Such may have been the fate of the fine individual of the
8. neogaeits, Lund, whose skull was found in Brazil by Lund, and
which is familiar to us through the figures of de Blainville."
MacJiaerodus is placed among the Eelidae on account of the
fact that the condyloid and carotid foramina unite with the
foramen lacerum posterlus. But as In at least one species,
Jú jpcdmidens, there is an alisphenoid canal, which, however, has
disappeared in the more recent American forms, it seems per-
missible to retain the genus in the family Machaerodontidae
though Its existence reduces the differential character of that
' to a minimum- The genus goes back to the Eocene.